Although it can be used in any navigation system, the present invention and the underlying problem are explained with reference to an on-board navigation system of an automobile.
Today's navigation systems are basically composed of the following subsystems: a digital road map, a system management unit itself, a position locator unit, a travel route determination unit, interfaces to the vehicle sensor system in order to detect vehicle movements, an input unit for operating the system, and an output unit for destination guidance, as well as a destination guidance unit and, optionally, a communications system for connection to external traffic information centers.
The digital road map is usually carried along on mass storage systems, normally CD ROMs, in the navigation system. The digital road map may contain road networks with varying coverage (for example, Germany only) or also varying details (for example, highway network and city street network of certain regions).
If the navigation system is activated, the driver can input his desired destination via keyboard and menu selection. After the position of the vehicle has been determined and entered into the system, the travel route determining unit initiates an algorithm which calculates an optimum route to the destination. The driver is essentially guided along this route to his destination.
In certain navigation systems the route can also be optimized according to certain parameters such as distance optimization or time optimization.
If the driver deviates from the precalculated route for any reason, such as not paying sufficient attention or, for example because he did not notice an exit sign, or due to other events such as encountering a construction site, a traffic jam, any other traffic problem or disturbance, a new route is calculated and the travel directions are generated anew.
Navigation systems also offer the possibility to dynamically take into account and respond to traffic problems reported via a traffic radio transmitter in the route planning. This results for example in updated route planning where a reported traffic jam is to be bypassed.
Decisions by the driver to deviate from the route proposed by the system based on his experiences, his intuition, or the spontaneous recognition of a certain traffic situation, however, do not enter in the route planning of the navigation system.
Previously such events could be neither input into the system nor evaluated for relevance as traffic problems in any manner. However, this would be extremely useful for such regions of the traffic networks for which insufficient traffic information is provided such as regional roads or state roads.